The beginning of a study represents for freshmen a difficult period of adjustment. Observations obtained in student counseling centers as well as in investigations of students' adjustment indicate that the beginning of a study represents for students a specific crisis period determined by dealing with the experiences of ‘psychological separation’. Therefore, the aim of the investigation was to prove the existence of a crisis period at the beginning of a study by investigating the change of students’ psychological adjustment and their use of defense mechanisms during their first year of study. In regard to this aim the task of the investigation was to examine I. the significance of differences in the level of psychological adjustment and defense mechanisms at the beginning and the end of the first year of study, and also II. the contribution and correlation of defense mechanisms to psychological adjustment. In this investigation were involved female freshmen (N=80) at the Department of Educational Sciences at the University Juraj Dobrila in Pula (Croatia). The obtained results confirm the existence of a crisis period at the beginning of a study. i. In the investigation a significant lower level of self-esteem and also a significant higher level of the use of defense mechanisms were obtained at the beginning than at the end of the first year of study. Also ii. In these different self-esteems, during the first year of study, different defense mechanisms had significant contribution. So at the beginning (in lower level of self esteem) a significant contribution had lower mechanisms, such as projection while at the end of the first year of study (in higher level of self esteem) a significant contribution had higher defense mechanisms such as reactive formations. iii. In the analysis of correlations among defense mechanisms and different levels of self-esteem the same results have been obtained so that at the beginning, significantly negative correlations had lower mechanisms, such as projection, regression and compensation, while at the end of the first year of study, excluding projection as lower mechanism, higher mechanisms had significant correlations, such as reaction formation and repression. These results contributed to the understanding specificities of initial studying and to developing appropriate psychological approaches in student counseling centers.